A severe limitation of grating based phase-contrast imaging systems, such as X-ray phase-contrast imaging systems for hard X-rays (15 to 30 keV), is that the system usually has to be designed for a certain mean energy EM. Consequently, such systems will use phase-information in a more or less narrow band with a bandwidth of approximately 10% around the design-energy. For mammography systems typical spectra are much wider in bandwidth and the necessary choice of design-energy may significantly limit the fraction of x-ray power in the spectrum contributing to the phase-contrast imaging process.